Ducted unit in chippy

[Climateman]

One of my customers wants me to install a 5kW ducted system in a chippy. Due to the grease he wants to supply 100% fresh air into the indoor unit. No recirc at all.

Sounds possible in theory as ambient air will be at a lower temp (and cleaner) than air in the chippy.

Has anyone done this before. The drawbacks I can forsee are freezing up due to running constantly and extra strain on plant. Thoughts?

[The Viking]

To answer your question first; Yes (but not in a chippie)

But you will probably not find an "off the shelf" unit that will do it for you.
My solution would be a bespoke made (small) AHU with a DX coil in it, depending on what system solution you go for this would also be able to heat the air in the winter (If we ever get another one) and yes even in a chippie there will be a heating demand on the fresh air.

Daikin (among others) makes a nifty interface so that you can use their outdoor units with any DX indoor coil.

And, remember, the stat has to be in the room, maybe together with a low limit sensor in the supply air.

One final thought, when you do your calcs remember to include for the fresh air load.

[Climateman]

Cheers Viking, a few things to think about there

[TRASH101]

you could still use an in void unit if you use an in line heater battery to temper the air in.
but if you do you will have to consider the following - dont use a heatpump,(if the indoor fan slows or stops heater might cut out),temperature control should be from the conditioned area,use the most basic indoor unit possible(cellar cooler basic so that compressor signal can be interrupted),low temp stat for evap protection and/or free cooling.
I could ramble on a bit more but wont

more detailed ramblings available if you like such things

[coolments]

Hi, another option is maybe you could install the indoor ducted unit in the back prep room or any where that the on air is cleaner and duct the air off into the counter to dishcharge via a double deflection or drum jet grilles.
If this is viable then dont forget a remote stat and air transfer grilles, this would save energy not having to run a heater to temper fresh air, I assume that by only installing a 5kw system they want to spot cool / heat the staff any way as chippy doors are always open. Just a thought.

[goodguy]

Sorry guys, What is a chippy? I'm Canadian eh!

[NH3LVR]

Sorry guys, What is a chippy?

Just a guess from someone who only speaks American.
A place that sells Fish and Chips?

[momo]

Chippie: traditional British fast food take away: deep frying of fish (cod/plaice/... in flour based batter) and chips... Experiments have led to the successful frying of pineapple rings, dried peas and chocolate bars - M*rs being a favourite...
Places get warm, greasy (a measure of quality and success) and humid hence need for cooling - in Summer? Any equivalent in Canada or other nations?
What area is to be cooled: work, office, store waiting area?
Apart from the above comments: Simple system or complex system that is the question, definitely with free-cooling. Simple single speed will need to be carefully sized to avoid stop/start and adequate distribution, complex with ducted inverter could be an option (T sensor on inlet and adjust temperature control to get a "balance" of cooled air into venue and heat load - it will also watch for freezing coil problem.)

[lana]

Hi Climateman,

As Viking said it should be done by an AHU with DX coil. There is nothing complicated about this but because there is only fresh air, then the load will be high.
On the other hand the summers there is not very hot or long. So I think with a quick estimate of the load you can design a fairly simple and practical unit.
Good Luck.
Cheers

P.S. have a fish&chips for me. I really missed it .

[coztemur]

When there is low ambient temperature and need of cooling, there is risk of liquid to compressor in your case.You could burn the compressor I think.
I suggest to use some capacity control or use small package liquid chiller.

Hi Climateman,

As Viking said it should be done by an AHU with DX coil. There is nothing complicated about this but because there is only fresh air, then the load will be high.
On the other hand the summers there is not very hot or long. So I think with a quick estimate of the load you can design a fairly simple and practical unit.
Good Luck.
Cheers

P.S. have a fish&chips for me. I really missed it .

[Andy W]

When there is low ambient temperature and need of cooling, there is risk of liquid to compressor in your case.You could burn the compressor I think.
I suggest to use some capacity control or use small package liquid chiller.

I thought exactly the same, I would fit a suction accumulator and control the evaporating temp with a hot gas capacity control valve such as a Danfoss CPCE and an LG mixer, but i bet the customer is after paying £399 B & Q prices knowing chip shops around my way!

[lana]

When there is low ambient temperature and need of cooling, there is risk of liquid to Compressor in your case.You could burn the Compressor I think.
I suggest to use some capacity Control or use small package liquid chiller.

Hi there,

This might not be relevant to this thread but I would like to point this out.

I have heard this statement many times but it is one of the miss-understanding, I am afraid.

I explain why.

When a system is designed for maximum ambient temperature and works properly, i.e. no liquid flood back to the compressor when ambient temp. is high, then there is no way that during low ambient liquid floods back.
The reason is very simple. TEV is selected for design pressure drops, i.e. max condensing. Now when ambient temp drops then condensing temp drops so would the pressure drop across TEV.
NOW with less refrigerant how can liquid flood back occur?

What actually happens which lead to this belief is this :
When pressure drop across TEV is decreased, the refrigerant mass flow decreases as well. This makes the suction pressure to decrease. If this makes the evaporating temperature to drop below 0°C then frost can be seen on the TEV and suction line. Therefore, some will miss-interpret this frost as liquid flood back.

Hope this will clear this point for some technicians.
Cheers

[DEVIL]

Whe did somth like that, with a duck, not in a "Chippie" (in Romania whe don't have stuff like that ) )
but in similar conditions, and the client whas whanting it cheep, so not a lot of options, so ...., whe did it with a duck unit, and a regulating dumper on the air flow, and whe did put a termostat (dono what brand, made in romania) that whas on the duct output, and whe did played a litle bit with the electronics on the duct, so whe don't kill the fan of the unit, and on the heeating, whe did add a'n aditional electric battery.
for protection of liquid back to compressor as coztemur sayd, whe added another termostat on the fresh air, when the fresh air is low, to just shut down the compressor, as u whouldn't need cooling

[DEVIL]

lana, not necesary, small units, non inverter, don't use TEV (inverter use EEV), they use capilary tube, and finaly even when there is no liquid back to compressor, the DX coil is geting frosted up, so air can't pass true, and the unit is useles

[lana]

lana, not necesary, small units, non inverter, don't use TEV (inverter use EEV), they use capilary tube, and finaly even when there is no liquid back to compressor, the DX coil is geting frosted up, so air can't pass true, and the unit is useles

Hi,

You are just confirming my point.
TEV or cap tube, no difference. If pressure difference across cap tube is decreased then the refrigerant mass flow decreases.
If there is no flood back to the compressor and the evaporator is frosted, then this means that the suction pressure is below 0°C.
Cheers

[DEVIL]

True , but it get's in a point where it whill never get out, the indor get's frosted, the temperature of the room, is not going to get down, so ... it's going to go forever, and, never defrost, because air conditioning, it's not ment fo freez.

So ... u need a protection for that.

and in the end, the frost on the indoor coil, it's not going to allow the refrigerent to change state, from liquid to gas , so , it's going to get beck to the compressor a mix, of liquid and gas, and if u have a long pipe length, u'r going to have a lot of refrigerent in the sistem, so ... the mix, is going to get ritche in liquid.

TEV, whill change the orifice, and allow lesss and less refrigerent.
But cap tube, whill allow the same amount - pressure drop changes, so ... TEV is mutch more eficient in this problem

Refrigerent it's not going to get in saturated liquid state back to the compressor, but a mix, and it's not healty

[lana]

You are absolutely right.

If the suction pressure goes down and the frost is built up on the evaporator then the problem becomes something else.

Now if the frost is too much then there will be liquid flood back to the compressor for the reason you mentioned : No evaporation in the evaporator. This is the reason of flood back not the low ambient temperature.
To put it in a simple words I should say that one problem leads to another.
Cheers

[Climateman]

Hi everyone, sorry I've been missing from this conversation for a while. Yes a chippie does sell fish & chips. Momo & Coolments - the intention is to spot cool staff. From most of the comments it looks like it is likely to freeze up for one reason or another. I think I will suggest putting the return grilles in the back prep area & deal with any grease build up.

PS Lana, fish & chips were good, feel fat now though.

[momo]

Recent, visit to a M*Dona's, (just to reset my taste buds ) led me to look at ceiling: public area ducted units, special line exit duct over cash tills pointing down/outward.

Question is: Is this a M*Dona's standard install?

Since this company, B*K'ng and other franchises standardize their operations and equipment.

Has anybody (not betraying contract secrecy clauses!!!) noticed design standards/fashions in fast food outlets ?

[momo]

Jollycold Thanks for the feedback.
Good principle: If it is simple and works - use it.

Are systems still fixed speed or is efficiency (inverter) technology creeping in ?